OF THE UNITED STATES. 11 



A white, soft limestone, not harder than some coarse 

 chalks, which it much resembles : replete with fossils. 



All these varieties are occasionally infiltrated by sili- 

 ceous matter, and considerable masses of chert are occa- 

 sionally observed in them : they also present some ap- 

 pearances of the green grains so characteristic of the 

 marls adjacent. 



GEOGRAPHICAL DISTRIBUTION, ORGANIC CHARACTERS &c. 



When my attention was first called to this subject, 

 eight years ago, I could not trace the ferruginous sand 

 beyond the peninsula of New Jersey, and a small part of 

 Delaware : subsequently, however, it has been discovered 

 in nearly all the southern states, and I now believe it to 

 be one of the most extensive formations on this continent. 



From the observations of Professor Hitchcock I have no 

 doubt that it forms the substratum of the islands of Nan- 

 tucket and Martha's Vineyard, on the coast of Massachu- 

 setts. Long Island will doubtless prove a link in the same 

 series. But this formation is first unequivocally recog- 

 nized in New Jersey, whence it may be locally traced 

 through Delaware, Maryland, Virginia, North and South 

 Carolina, Georgia, Alabama, Mississippi, Tennessee, Lou- 

 isiana, Arkansas and Missouri. 



These various deposits, though seemingly insulated, 

 are doubtless continuous, or nearly so, forming an irregu- 

 lar crescent nearly three thousand miles in extent ; and 

 what is very remarkable, there is not only a generic ac- 

 cordance between the fossil shells scattered through this 

 vast tract, but in by far the greater number of compari- 



